It is known to produce composite molded articles by fitting a sheet to an injection mold and then injecting a thermoplastic resin into the mold. In this technique, the sheet can be fitted in a cavity of the mold by mere insertion, or by means of insert pins, or by vacuum suction. The sheet fitted by mere insertion, unless having a specific size or shape, is liable to move out of position with the flow of the injected resin. The sheet fitted by means of insert pins, unless having a specific size or shape, is liable to suffer wrinkling due to the flow of the injected resin and thermal contraction.
On the other hand, when the fitting method by vacuum suction (hereinafter referred to as vacuum method) is applied to production of large-sized articles or articles having a curved surface, a gap may be formed between the sheet and the mold due to the shock or vibration on mold closing to reduce the sucking force. If a resin is injected under such a state, the sheet is shifted out of its proper position or suffers wrinkling, or the sheet is expanded or contracted due to the heat of the injected resin to cause wrinkling. When the article has a curved surface, it is difficult to fit the sheet, particularly its end portions, intimate to the mold because of its rigidity. Even if the sheet is once fitted, the same problem as stated above is apt to arise. Further, since the vacuum method essentially requires a mold having special vacuum ports for suction on the inner wall and vacuum-lines in the inside, the mold is expensive and the operation is complicated.
In addition, it is difficult to automate the sheet fitting in the mold by means of pins or by the vacuum method because robots or the like automatic systems are extremely incompetent in this field.